Tellurium (Te) fed to rats beginning on the 15th postnatal day (PND), and daily afterwards, results about 3 days later in a complete paralysis of the hind legs and severe segmental demyelination of the sciatic nerve. These events are taking place during myelinogenesis of the sciatic nerve. In spite of the continued ingestion of the Te there is complete clinical recovery and disappearance of demyelination 7 to 10 days later. After stoppage of Te ingestion on the 30th PND and until the 120th PND - the end of our study - the sciatic nerve of the Te-fed rats appears morphologically normal but the motor nerve conduction time is slower and there are few myelinated fibers than the normal sciatic nerve. The purpose of this project is to localize the Te in the sciatic nerve periodically, at successive stages of the pathology and recuperation caused by ingestion of Te. The methods of study are: 1. The tracing of the morphological and physiological pathways of the Te with the electron microprobe; 2. The quantitation of the Te with the atomic spectrophotometer; 3. The physiological study of motor nerve conduction velocity of the nerve; 4. The counting of nerve fibers in the nerve. The aim of the project is to study the role of Te during Te-induced neuropathy and its recuperation. The overall objective is to obtain information concerning this neuropathy occurring during myelinogenesis and obtain information concerning the vulnerable period of development of the peripheral nervous system.